The present invention relates to a device for determining the mean resistivity of a multiphase fluid having a continuous conductive phase, and more particularly it relates to such a device having a segment of insulating pipe and means for generating an electric current in the fluid flowing along said pipe. The invention also relates to a device for determining the volume fraction occupied by a resistive fluid in a multiphase fluid having a continuous conductive phase, and also to a method of determining the mean resistivity of such a fluid.
Document FR-A-2 780 499 discloses devices for characterizing the flow of a multiphase fluid, using capacitive sensors. Such devices serve in particular to determine the dielectric constant of an insulating fluid and to deduce therefrom the volume fractions of the two phases when the fluid is a two-phase fluid. These devices can provide satisfactory results, but cannot be used with a multiphase fluid in which the conductive phase is continuous since the fluid is then no longer insulating. This occurs, for example, in a well for extracting hydrocarbons when the water fraction exceeds a certain value.
Document FR-A-1 307 879 discloses a device for measuring flowing fluids in a pipe having an insulating liner. Current source and measurement electrodes are placed inside the liner in contact with the flowing fluid in order to make the measurements
Characterizing devices are also known that comprise a segment of insulating pipe and means for generating an electric current in the fluid flowing in said pipe. These devices thus complement the preceding devices since they apply to multiphase fluids having a continuous conductive phase, i.e. fluids that are not insulating.
The difficulty with the latter devices lies in measuring the potential difference between two points of the fluid to deduce the electrical resistance between said two points, given knowledge of the current. Thereafter, said resistance is used to deduce the mean resistivity given that the shape of the pipe is known.
The present invention seeks to provide means enabling such a measurement to be performed.
More particularly, the invention seeks to provide such means that are insensitive to corrosion and to the surface state of the inside face of the wall of the pipe.